Process for acetylating olefines



Jan. 17 1933. B. T. BROOKS 1,894,562

PROCESS FOR ACETYLATING OLEFINES Filed May 6, 1950 Y5 wmi g Patented, Jan. 17, 1933 umrao STATES PATENT OFFICE BENJAMIN BROOKS, OF GREENWICH, CONNECTICUT, ASSIGNOB T PETROL! CHEMICAL CORPORATION, A CORPORATION OF DELAWARE PROCESS FOR ACEIYLATING OLEFINES Application filed. May 6,

This invention relates specifically to the art of acetylating olefines occurring in mixtures v of hydrocarbons produced by cracking petroleum oil by causing the said olefines to 6 combine directly with acetic acid. The invention will be fully understood from the following description read in conjunction with the drawing which is a diagrammatic elevation with parts in section of apparatus in 10 which my invention may be carried into effeet.

The phrase petroleum oil as herein employed, denotes generically a crude petroleum and/or the normally liquid distillates derived therefrom. When such petroleum oil is cracked to produce gasoline, a complex series of hydrocarbons is produced ranging from hydrocarbons corresponding to the oil charged, up to and including methane, and in particular where the cracking is relatively extensive as, for example, cracking carried out at relatively high temperatures in liquid phase under high pressures or in vapor phase at any pressure. In the case of vapor phase cracking carried out, for example, between l050-and 115 0 F., products'consist predominately of olefines. Olefines so produced have heretofore been acetylated by causing acetic acid to combine directly with a fraction separated from the products of cracking which fraction contained a variety of olefines of diiferent molecular weights, thereby producing a mixture of acetic acid esters with different alkyl radicals. It has also been proposed to separate from said mixtures of hydrocarbons a fraction containing butylenes,.amylenes and hexylenes, and to cause the olefines in such fraction to combine directly with acetic acid. In the latter case, the removal of the tertiary olefines has been proposed as a preliminary step of the acetylation of the secondary olefines, and it has also been proposed to polymerize and separate diolefines. I have found that the preliminary removal of the diolefines by polymerization invariably involves a loss of very substantial quantities of the secondaryolefines either chemically or physically, and I have correspondingly found that I can very substantially improve the acetylation efiiciency 1930. Serial No. 450,265.

by preliminarily removing the diolefines in unpolymerized condition. I have further found that the efiiciency obtained when directly acetylating olefines can be very substantially improved by separating the original mixture of olefines into fractions containing predominately olefines of a single number of carbon atoms to the molecule and reacting with aceticacid on the fraction so separated. It is of specific advantage in this case to separate the tertiary olefines before acetylating secondary olefines, and I further find that by physlcally separating the mixture into fractions, selectively removin unpolymerized diolefines and tertiary ole nes from the as separated fractions, I am enabled to obtain practically quantitative yields of the esters of the secondary olefines. This represents a very substantial increase in efiiciency over that obtainable by the processes previously disclosed. My process is particularly applicable to the generation of acetic acid esters in which the alkyl radical contains from 3 to 7 carbon atoms both inclusive.

The invention will be illustrated by a specific example in which the raw material taken is the light ends of the hydrocarbons produced by vapor phase cracking of petroleum, containing hydrocarbons up to and including compounds of 5 carbon atoms to so the molecule. The process is applicable to the acetylation of olefines of higher molecular weight, but the process may be fully illustrated by application to the olefines up to 5 carbon atoms to the molecule. The mixture of hydrocarbons is introduced through pipe 1 to the rectifying column 2, which may be of any suitable construction and is operated to separate a bottoms consisting predominantly of hydrocarbons of 5 carbon atoms to the molecule. This is withdrawn through pipe 3 controlled by valve 4 and retained in storage tank 5. The overhead substantially free from hydrocarbons of 5 carbon atoms to the molecule passes off through pipe (icon trolled by valve 7 and is compressed in 8, and supplied thereby to rectifying column 10 which may be of any suitable construction.

Column 10 is operated to produce a bottoms consisting predominantly of hydrocarbons of 4 carbon atoms to the molecule. The )ressure within the column may be regulated by corresponding temperature control; but whereordinary cooling water is employed in refluxing the column is necessarily operated under pressure; although in this case the necessary pressure will not ordinarily exceed 100 pounds to the square inch. The bottoms is withdrawn through pipe 11 controlled by valve 12 and retained in storage tank 13. The overhead substantially free from hydrocarbons 0t 4 carbon atoms to the molecule passes oil through pipe 14 controlled by valve 15 to compressor 10, by which it is supplied to rectifying column 20. The reflux in column 20 may also he provided by the use of ordinary cooling-water and the column is in this case operated under pressures which will not ordinarily excced300 pounds to the square inch. f 7

Column 20 is operated to produce a bottoms consisting predominantly of hydrocarbons of 3 carbon atoms to the molecule which is withdrawn through pipe 21 controlled by valve 22 and retained in storage tank .23. The remanent gas substantially free from lydrocarbons of 3carbon atoms to the molecule is diverted from the system through pipe 24 controlled by valve 20. The amylene fraction in =tauk Trwill. in this case, consist predominantly of olefines; of various types including both tertiary and dioletines. This fraction is first treated to separate diolefiiies therefrom and preferably to separate the major part of the diolefines'in unpolymerized condition. This may be accomplished by alternative methods, although one preferred method consists in introducing a quantity of the hydrocarbon material from tank 5 through pipe 31 controlled by valve 32 to autoclave 33, and admixing it in 33 at relatively low temperatures with a slurry of cuprous chloride in water containing ammonium chloride. The ten'iperature during this operation preferablyheld below 10 C. by circulating a cooling or refrigerating medium through the jacket 34 by means of pipes and 36 which are provided for this purpose. Mixing is accomplished by rotation of propeller 37. The slurry of water containing cuprous chloride in 33 preferably contains from 5 to 20 parts of ammonium chloride for every 100 parts of H 0 present. The cuprous chloridis preferably in excess over that required to combine with all the diolefines present, After agitating the materials together, say for example one hour, the rotation of propeller 37 is discontinued and the materials in 33 are permitted to settle. The remanent hydrocarbon substantially free from diolefinesis then withdrawn through side arms 38 controlled by valves 38". The cuprous chloride diolefine mixture in 33 may be regenerated for reuse by heating, and the diolefine may be recovered and withdrawn through pipe 39 controlled by valve 40.

The remanent hydrocarbon mixture With- I drawn through one of the side arms 38 is diverted into autoclave 41 and is treated therein with aqueous sulphuric acid preferably of from 55 to 65%, H 50 content, while maintaining temperatures below 25 C. and preferably below 20 C. by circulating a cooling medium through jacket 42 by use of the pipes 43 and 44 communicating therewith. The sulphuric acid is preferably present in quantity suflicient to combine with all the tertiary olefines present and the hydrocarbon mixture is thoroughly mixed with the acid by rotation of propeller 45. After mixing the materials for a suitable period, for example one hour, settling is permitted for an additional period which may conveniently be one or two hours, and the lower layer containing tertiary alkyl sulphate is withdrawn through pipe 50 controlled by valve 51, and diverted from the system through pipe 52 controlled by valve 53 to be worked up for tertiary alcohol.

"Any alternative method of separating the tertiary oletincs may be resorted to including, for example, the use of muriatic acid. The remanent hydrocarbon material in 41, which is now substantially free from both di and tertiary olefines, is now run into autoclave 60 through pipe 50. This hydrocarbon material now consists predominantly of secondary olefines of 5 carbon atoms to the molecule There is added to the material in autoclave 6O sufficient acetic acid, preferably glacial acetic to react with the amylene present together with about 5% of 96%, H 80 by weight, based on the acetic acid present. The materials are mixed by rotation of propeller 61 and preferably warmed to temperatures between 100 and 130 C. by the introduction of a heating medium to jacket 62 by means of pipes 63 and 64 communicating therewith. The mixing should be continued for a period of several hours, preferably for a period of 24 hours. At the expiration of the mixing period, sodium acetate is preferably added in.

quantity sufficient to neutralize the H SO added. The material may be filtered, if desired, to remove any sodium sulphate formed and is preferably distilled to separate the 'amyl ester of acetic acids from any other materials present such as, for example, saturated hydrocarbons, unconverted olefines, and/or acetic acid.

The hydrocarbon material in tank 13 will consist predominantly of olefines of 4 carbon atoms to the molecule where the raw material is produced by vapor phase cracking, and will contain both tertiary and diolefines in addition to the secondary olefines. While I may admix this material with acetic acid and acct late directly in this manner, I find it pre erable to preliminarily remove the tertiary and/or diolefines. The diolefines, for

best results, must be removed in un lymerized condition-inasmuch as I have mind that their removal by olymerization involves the simultaneous estruction and re- 5 moval of substantial quantities of the secondary olefines. Material from 13 is diverted through pipe controlled by valve 71 to the autoclave 72. Autoclave 72 is preliminarily charged with a slurry of cuprouschloride in water preferabl containing ammonium chloride corresponding to the material charged to autoclave 33. The hydrocarbon material is admixed with the on rous chloride slurry by rotation of propeller 7 3, and during this stage the temperature is preferably held below 10 C. by the introduction of a refri erating medium to the jacket 7 4 by means 0? the pipes 75 and 76 communicating therewith. At'the expiration of a suitable period for substantial complete reaction, the stirring is discontinued and the material in 72 is permitted to settle. The amount of cuprous chloride charged to 72 should, of course, be sufficient to combine with all of the diolefines present, a slight excess being preferred.

The remanent hydrocarbon material, on settling, forms an upper layer which may be decanted by means of the side arms 80 controlled by valves 80, and the cuprous chloride diolefine compound remaining in 72 may be regenerated, for example, by heating with the consequent recovery of the separated diolefine which may be taken off in vapor phase through the outlet 76 controlled by valve 77. The hydrocarbon material from pipe 80 is discharged into autoclave in which it is treated with dilute aqueous sulphuric acid, preferably of from 55 to 65%, H SO, content. The temperature during this stage should not exceed 25 C., and for best results should not exceed 20 C. The amount of acid present should be at least sufiicient to combine with all the tertiary olefines present, a slight excess of acid, say from 5 to 10%, being preferred.

Mixing is accomplished during this stage by rotation of propeller 91 and temperature control is effected by circulatinga cooling medium through jacket 92 by means of the pipes 93 and- 94 communicating therewith.- A suitable mixing time would be approximately one hour, and at the expiration of this period the materials in 90 are permitted to settle, say for one or two hours. During the treatment with sulphuric acid for removal of the tertiary olefin'es as carried out in autoclave 90 on the hydrocarbon material of 4 carbon atoms-to the molecule, oras carried out in autoclave 41 on the hydrocarbon material of 5 carbon atoms to the molecule, a sulphuric acid may be added to the hydrocarbon material in a relatively small stream; or contersely, the hydrocarbon material may be gradually added in a relatively small stream to the acid material. The gradual introduction of one reacting material into the other facilitates tem erature control.

At the expiration of t e settlin time, the lower layer consisting principal y of tertiary butyl sulphate ma be withdrawn through pipe controlle by valve 101, and diverted from the system through side arm 102 controlled by valve 103. The remanent hydrocarbon material is then discharged into autoclave in which it is admixed in liquid phase with glacial acetic acid in'quantity substantially suflicient to combine with the secondary olefine present. A small quantity of 98%, H 80 for example 1% by weight of the acetic acid present is preferably introduced as a catalyst. The

materials are mixed by rotation of propeller 111 and heated by the introduction of a heating medium to jacket 112 by means of pipes 113 and 114 communicating therewith. A

period of about twenty-four hours may be allowed for the reaction between the secondary olefine and acetic acid. At the expiration of such time, a small quantity of sodium acetate may be introduced throu h pi e controlled by valve 121 to neutralize t e H SO present. The butyl ester of acetic acids so produced may be withdrawn through pipes controlled by valve 131. It is preferably filtered to separate any precipitated sodium sulphate and distilled to se arate the butyl ester of acetic acid from ot er materials such as saturated hydrocarbons, unconverted secondar olefines, and/or acetic acid.

The hydrocarbon material in storage tank 23 consisting of hydrocarbons of 3 carbon atoms to the molecule will consist predominantly of propylene, inasmuch as the raw material was produced by vapor phase cracking and may contain propadiene. This material may conveniently be discharged through pipe controlled b valve 141 to the autoclave 150. Acetic aci preferably glacial, corresponding to the ropylene present may be introduced throng pipe 151 controlled by valve 152. The reactlng materials are mixed by rotation of pro eller'153. The propylene is held in liquid p ase during this treatment and the materials in are heated by the introduction of a heating medium to jacket 151 by means of pipes 152 and 153. At the expiration of a suitable time say for example twenty-four hours, the H S O, present may be neutralized by the addition of sodium acetate and the material ma be withdrawn through pipe controlled by valve 171. It is preferably filtered to separate any precipitated sodium sulphate and distilled to separate the propyl ester of acetic acid from any other materials resent.

-The foregoin specific escri tion is furnished by way 0 illustration an not of limitation. The invention is susce tible of being carried out in a variety of mo ifications, and for this reason it is my intention thatthe invention be limited only by the following claims or their equivalents in which I have endeavored to claim broadly all inherent novelty.

' I claim:

1. In the process of generating secondary butyl and amyl acetates from a mixture of hydrocarbons produced by cracking petroleum oil, the steps of separating from said mix- 119 ture by distillation a fraction, the olefine content of which consists predominantly of olefines of the same number of carbon atoms to theinolecule corresponding to the acetate to be produced, and thereafter esterifying the secondary olefines contained in said separated fraction by admixing the said fraction with free acetic acid and a catalyst.

2. In the process of generating secondary butyl and amyl acetates from a mixture of hydrocarbons produced by cracking petroleum oil, the steps of separating from said miX-. ture by distillation a fraction, the olefine content of which consists predominantly of secondary, tertiary and diolefines of the same number of carbon atoms to the molecule corresponding to the acetate to be )roduced, se-

lectively removing tertiary olefines and unpolymerized diolefincs from said fraction, and

thereafter esterifying the secondary olefines contained in said separated fraction by admixing the said fraction with free acetic acid and a catalyst.

3. In the process of generating secondary butyl acetate from a mixture of hydrocarbons produced by cracking petroleum oil, the steps of separating from said mixture by distillation afraction, the olefine content of which consists predominantly of olefines of 4 carbon atoms tothe molecule, and thereafter esterifying the secondary olctines contained in said separated fraction by admixing the said fraction with free acetic acid and a catalyst. 4. In the process of generating secondary butyl acetate from a mixture of hydrocarbons produced by cracking petroleum oil, the steps of separating from said mixture by distillation a fraction, the olefine content of which consists predominantly of secondary, tertiary and diolefines of 4 carbon atoms to the molecule, selectively removing tertiary olefines and unpolymerized diolefines from said fraction, and thereafter esteritying the secondary olefines contained in said separated fraction by admixing said fraction with free acetic acid and a catalyst.

5. In the process of generating secondary hutyl or amyl acetates from a mixture of hydrocarbons produced by cracking petroleum oil and containing secondary, tertiary and diolefines, the steps of selectively separating from said mixture tertiary olefines and unpolymerized diolefines, and thereafter esteritying the said secondary olefines by admixing the same with free acetic acid and a catalyst.

,65 BENJAMIN '1. BROOKS. 

